Memory is one type of integrated circuitry, and is used in computer systems for storing data. Integrated memory is usually fabricated in one or more arrays of individual memory cells. The memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
Integrated circuitry fabrication continues to strive to produce smaller and denser integrated circuits. The smallest and simplest memory cell will likely be comprised of two electrically conductive electrodes having a programmable material received between them. Suitable programmable materials have two or more selectable resistive states to enable storing of information by an individual memory cell. The reading of the cell comprises determination of which of the states the programmable material is in, and the writing of information to the cell comprises placing the programmable material in a predetermined resistive state.
Significant interest is presently being directed toward programmable materials that contain mobile ions as charge carriers (such programmable materials may be referred to as ion-mobility-based programmable materials). The ion-mobility-based programmable materials may be converted from one memory state to another by moving the mobile charge carriers therein to alter a distribution of charge density within the programmable materials. Some example memory devices that utilize ions as mobile charge carriers are resistive RAM (RRAM) cells; which can include classes of memory cells containing multivalent oxides, and which can include memristors in some specific applications. Other example memory devices that utilize mobile ions as charge carriers are programmable metallization cells (PMCs); which may be alternatively referred to as a conductive bridging RAM (CBRAM), nanobridge memory, or electrolyte memory.
The RRAM cells may contain ion-mobility-based programmable material sandwiched between a pair of electrodes. The programming of the RRAM cells may comprise transitioning the programmable material between a first memory state in which charge density is relatively uniformly dispersed throughout the material and a second memory state in which the charge density is concentrated in a specific region of the material (for instance, a region closer to one electrode than the other). A PMC cell may similarly have ion-mobility-based programmable material sandwiched between a pair of current conductive electrodes. However, programming of the PMC comprises transitioning the PMC between a first state in which there is no conductive bridge between the electrodes and a second state in which mobile ions arrange to form super-ionic clusters or conducting filaments that electrically couple the electrodes to one another.
In some applications, there can be advantages to having one or both of the electrodes of a memory cell comprise platinum. For instance, some ion-mobility-based programmable materials comprise a combination of Pr, Ca, Mn and O (so-called PCMO, which may be, for example, Pr0.7Ca0.3MnO3), and it can be advantageous to have such programmable materials be directly against a platinum electrode.
Difficulties are encountered in forming platinum electrodes, in that platinum is a noble metal and can be difficult to pattern. It would be desirable to develop new methods for incorporating platinum electrodes into memory cells, and new memory cell architectures which include ion-mobility-based programmable materials in combination with at least one electrode.
Platinum may have other applications in integrated circuitry in addition to, or alternatively to, the utilization of platinum as an electrode of a memory cell. For instance, platinum may be utilized as electrically conductive contacts or interconnects in integrated circuitry. It would desirable to develop methods of patterning platinum that could be suitable to fabricate platinum into electrically conductive contacts or interconnects.